1. Field of Invention
The present invention relates, in general, to chemical compounds having antiproliferative and antimitotic activity. More specifically, the present invention is directed to novel 2-alkoxy estradiols having antiproliferative and antimitotic activity and to methods of preparing and using these novel compounds.
2. Description of the Related Art
Certain 2-alkoxy estradiols have been discovered to have antitumor activity (U.S. Pat. No. 6,136,992; U.S. Pat. No. 6,054,598; U.S. Pat. No. 6,051,726; U.S. Pat. No. 5,892,069; U.S. Pat. No. 5,661,143; U.S. Pat. No. 5,504,074; WO 95/04535) (all patents cited throughout this specification are incorporated herein by reference). 2-Methoxyestradiol (2-ME2) is one such 2-alkoxy estradiol exhibiting antitumor activity (U.S. Pat. No. 5,892,069; U.S. Pat. No. 5,661,143; U.S. Pat. No. 5,504,074; WO 95/04535). 2-Methoxyestradiol is an endogenous mammalian metabolite formed by the sequential biochemical hydroxylation and methylation of the natural hormone estradiol (Breuer, H. et al., Naturwissenschaften 12, pp. 280-281 (1960)).
Recent studies have demonstrated that the mechanism responsible for the antitumor activity exhibited by certain 2-alkoxy estradiols, including 2-ME2, includes interference with or prevention of cell mitosis, the multi-step process that preceeds cell division and replication (Alberts, B. et al., The Cell, pp. 652-661 (1989); Stryer, L., Biochemistry (1988)). For example, some 2-alkoxy estradiols have been shown to inhibit the replication of certain cancer cells by interfering with microtubule formation and function (Seegers, J. C. et al., J. Steroid Biochem. 32, pp. 797-809 (1989); U.S. Pat. No. 6,136,992; U.S. Pat. No. 6,054,598; U.S. Pat. No. 6,051,726; U.S. Pat. No. 5,892,069; U.S. Pat. No. 5,661,143; U.S. Pat. No. 5,504,074; WO 95/04535). Microtubules facilitate and make possible, among other things, chromosome and organelle movement and segregation during cell mitosis (Stryer, L., Biochemistry (1988)). Preventing or interfering with microtubule formation and function leads to mitotic arrest and frequently to apoptosis. In addition to cancer, many diseases are characterized by undesirable cell proliferation, and the value of compounds and methods that prevent such undesirable cell proliferation is of great importance to the treatment of such diseases. Microtubule formation and function is also critical to cell maintenance, locomotion and the movement of specialized cell structures such as cilia and flagella (Stryer, L., Biochemistry (1988)).
To function properly, cilia and flagella require proper tubulin polymerization (U.S. Pat. No. 6,162,930). Certain 2-alkoxy estradiols are known to inhibit tubulin polymerization or to cause the formation of tubulin polymer with altered morphology and stability properties (U.S. Pat. No. 6,136,992). By interfering with normal microtubule dynamics, such compositions may be used to treat those diseases characterized by abnormal proliferation.
Certain 2-alkoxy estradiols, including 2-ME2, have also been demonstrated to act as antiangiogenic agents (Fotsis et al., Nature 368, pp. 237-239 (1994); U.S. Pat. No. 6,136,992; U.S. Pat. No. 6,054,598; U.S. Pat. No. 6,051,726; U.S. Pat. No. 5,892,069; U.S. Pat. No. 5,661,143; U.S. Pat. No. 5,504,074; WO 95/04535). Such antiangiogenic activity is likely due to the arrest of endothelial cell mitosis and the consequent prevention of endothelial cell proliferation. 2-alkoxy estradiols exhibiting antiangiogenic activity may be used to treat diseases in which angiogenesis plays an important role. Inducing mitotic arrest and preventing angiogenesis will cause tumors to shrink, and the combination of these methods will provide significant advantages over current anticancer therapies. 2-alkoxy estradiols in murine models have been shown to be orally active, and to exhibit no appreciable toxicity at therapeutically effective doses (Fotsis et al., Nature 368, pp. 237-239 (1994)).
In general, there is a need in the art to identify additional antiproliferative and antimitotic chemical compounds which provide therapeutic advantages over those compounds currently known and used. Additionally, there is a need to improve the method of synthesis of such compounds in order to provide greater efficiency, yield, and purity in their production.
The present invention is directed to novel 2-alkoxy estradiols and derivatives of 2-alkoxy estradiols having antiproliferative and antiangiogenic activity. The invention is also directed to methods of preparing and using these novel compounds.
One embodiment of the present invention are compounds represented by the following structural formulas: 
Wherein
R1 is (C1-6) alkyl, and optionally substituted by halogen;
R2 is H, or SO2NHR, with R being hydrogen or (C1-6) alkyl;
R3 is selected from the group consisting of hydrogen and (C1-6) alkyl, and optionally substituted by halogen;
R4 is hydrogen, (C1-6) alkyl, (C2-6) alkenyl, (C2-6) alkynyl, aryl or heteroaryl;
R5 is (C1-2) alkyl;
R6 is O, NOR, (H, OR), or (H, OSO2NHR), wherein R is hydrogen, (C1-6) alkyl or (C1-6) acyl.
R7 is hydrogen or (C1-6) alkyl;
The invention includes pharmaceutically acceptable salts or esters, prodrugs and precursors thereof, in admixture with one or more pharmaceutically acceptable carriers, diluents, or excipients therefor.
The term (C1-6) alkyl means a branched or unbranched alkyl group having 1-6 carbon atoms. Likewise the term (C1-2) alkyl means methyl or ethyl.
The term (C2-6) alkenyl means a branched or unbranched alkenyl group having at least one double bond and 2-6 carbon atoms.
The term (C2-6) alkynyl means a branched or unbranched alkynyl group having at least one triple bond and 2-6 carbon atoms.
The term aryl means a phenyl group, either unsubstituted or monosubstituted, with groups chosen from (C1-6) alkyl, (C2-6) alkenyl, (C2-6) alkynyl, OR, NHR or NR2, with R being hydrogen or (C1-6) alkyl. Preferred aryl groups are substituted in the para position. The term heteroaryl means a heterocyclic aromatic group such as furanyl, pyrroyl, pyridinyl or thiofuranyl either unsubstituted or monosubstituted, with groups chosen from (C1-6) alkyl, (C2-6) alkenyl, (C2-6) alkynyl, OR, NHR or NR2, with R being hydrogen or (C1-6) alkyl.
The term (C1-6) acyl means an acyl group derived from a carboxylic acid having 1-6 carbon atoms.
The term halogen means fluorine, chlorine, bromine, or iodine. Unless noted otherwise, the steroids of this invention have the natural configuration at chiral carbons, that is 8xcex2, 9xcex1, 13xcex2, and 14xcex1. The steroids of this invention may possess also one or more additional chiral carbon atoms. The compounds may therefore be obtained as a pure diasteriomer, or as a mixture of diasteriomers. Methods for obtaining the pure diasteriomers are well known in the art, e.g. crystallization or chromatography.
It is believed by the inventors that by incorporating a double bond in a strategic location in the molecule, such as for example the placement of the double bonds in Formulas I-III above, the conformational change thereby imparted to the molecule may play a significant role in the activity exhibited by the resulting compounds.
Another embodiment of the present invention are novel methods of preparing 2-Methoxyestradiol and 2-Alkoxyestradiol.
Another embodiment of the present invention is a method of making a medicament which is capable of inhibiting undesired cell proliferation, said medicament comprising, in a pharmaceutically acceptable carrier, a cell proliferation inhibiting compound as represented by Formula I, II, III or IV.
Another embodiment of the present invention is a method of treating an individual with cancer. The method comprises administering to the individual a therapeutically effective amount of a compound as represented by Formula I, II, III or IV, or a pharmaceutically acceptable salt thereof. Such treatment may be applied alone or in combination with other therapeutic modalities (e.g., surgery or radiation therapy).
Another embodiment of the present invention is a method of treating an individual with disease(s) characterized by undesirable cell proliferation. The method comprises administering to the individual a therapeutically effective amount of a compound as represented by Formula I, II, III or IV, or a pharmaceutically acceptable salt thereof.
Another embodiment of the present invention is a method of inhibiting cell proliferation. The method comprises contacting the cell, tissue or organ in which cell proliferation is not desired with an effective amount of a compound as represented by Formula I, II, III or IV, or a pharmaceutically acceptable salt thereof.
Another embodiment of the present invention is a method of treating an individual with disease(s) characterized by undesirable angiogenesis. The method comprises administering to the individual a therapeutically effective amount of a compound as represented by Formula I, II, III or IV, or a pharmaceutically acceptable salt thereof.
Another embodiment of the present invention is a method of inhibiting angiogenesis. The method comprises contacting the cell, tissue or organ in or from which angiogenesis is not desired with an effective amount of a compound as represented by Formula I, II, III or IV, or a pharmaceutically acceptable salt thereof.
Another embodiment of the present invention is a method of inhibiting microtubule formation and function. The method comprises contacting cells, tissues or organs in which microtubule formation and function is to be inhibited by an effective amount of a compound as represented by Formula I, II, III or IV, or a pharmaceutically acceptable salt thereof.
The disclosed novel compounds have activity against a variety of tumor cell lines, including ovarian and breast carcinoma, and against proliferation of endothelial cells. These compounds and their use may provide advantages over 2-ME2 and other non-endogenous 2-alkoxyestradiols currently known, and have the potential to be new antitumor, anticancer, anti-microtubule and antiangiogenesis drugs. Additionally, the compounds of the present invention can be used in combination therapy with other known chemotherapeutic or antineoplastic agents (e.g., alkylating agents, antimetabolites, antitumor antibiotics (e.g., vinca alkaloids and taxanes), hormones (e.g., tamoxifen), Selective Estrogen Receptor Modulators (SERMs), antibodies (e.g., Herceptin), and platinum coordination complexes, etc.).